This invention relates to optical switches and in particular to providing an optical switch having reduced insertion loss.
In optical communication systems it is often necessary to switch an optical signal between different optical paths, be it along a waveguide or in free space. Different categories for switching optical signals include electrical switches, solid-state switches, mechanical switches, and optical switches and combinations therebetween.
Mechanical optical switches are usually lower in cost than electrical or solid-state optical switches. They further provide low insertion losses and are compatible with the bandwidth of fiber optics. However, switching speeds of mechanical switches are relatively slow.
Solid-state optical switches have relatively fast switching speeds and the same bandwidth capacity as fiber optics. Unfortunately, the cost for these switches is much higher than for traditional mechanical switches and the insertion losses exceed those for existing mechanical switches.
Electrical switches also operate faster than traditional mechanical switches but their cost is also significantly higher. Furthermore, the switching of optical signals using electrical switches can not make use of the full optical bandwidth available with fiber optics.
As of late, developments in network systems, for example, have brought about the need for fast optical switches with low insertion losses. In addition, the need for reliable, low cost switches increased the development of mechanical optical switches having low insertion losses.
An exemplary mechanical optical switch that reduces or eliminates disadvantages and problems with prior art mechanical optical switches is disclosed in U.S. Pat. No. 5,444,801 to Laughlin incorporated herein by reference. The invention described therein teaches an apparatus for switching an optical signal from an input optical fiber to one of a plurality of output optical fibers. This apparatus includes means for changing the angle of the collimated beam with respect to the reference so that the output optical signal is focused on one of the plurality of output optical fibers. Similar mechanical optical switches are disclosed in U.S. Pat. No. 5,647,033 and U.S. Pat. No. 5,875,271 to Laughlin incorporated herein by reference.
Although optical switches disclosed in the prior art fulfill the need for low cost, reliable, and fast optical switches it is still desirable to improve the insertion losses encountered in prior art switches.
It is therefore an object of the invention to provide a mechanical optical switch having minimum insertion loss.
Further, it is an object of the present invention to establish conditions for optimum design of mechanical optical switches such that the insertion losses are minimized.
In accordance with the invention there is provided an optical deflection switch comprising: a) a switching block of light-transmissive material having a reflective surface and a second face, the second face including an input/output port and the reflective surface for providing reflection of a beam of light passing through the input/output port into the switching block; b) a second block of light-transmissive material having a first and a second face, the first face including an input port thereon for receiving a collimated beam of light and the second face for providing total internal reflection of the beam of light in a first switching state and for acting as an output/input port for optical communication with the input/output port of the switching block when the total internal reflection is frustrated in a second switching state, and an angle defined between the reflective face of the switching block and the second face of the second block being such that a normal to the reflective surface of the switching block bisects another angle defined between a beam passing into the switching block from the second block and a beam reflected from the reflective surface of the switching block; and c) a switch for selectively switching the device from the first switching state to the second other switching state.
In accordance with the invention there is further provided a method for designing an optical deflection switch comprising the following steps: a) providing a first refractor; b) providing an input port disposed in a first location and orientation relative to the first refractor; c) tracing a central light ray from the input port through the optical deflection switch in a first switching state wherein internal reflection of the light ray within the first refractor occurs, said central light ray being at the center of an optical beam, said optical beam being launched into the optical deflection switch at said input port; d) positioning a first output port to receive the reflected central light ray in the first switching state; e) providing a second output port to receive a reflected central light ray in a second switching state; and f) determining a thickness and an angle between two faces of the second refractor, said step comprising the following steps: determining a forward ray by tracing the central light ray from the input port through the first refractor and into a medium having similar optical properties to a second refractor; determining a backward ray by tracing the central light ray from the second output port through the first refractor and into a medium having similar optical properties to the second refractor; determining a point where the forward ray and the backward ray intersect; providing a second refractor having said point being disposed at a face of the second refractor for providing internal reflection when total internal reflection within the first refractor is frustrated, the angle defined between the two faces from which internal reflection occurs being such that a normal to the face where reflection is occurring when total internal reflection within the first refractor is frustrated, bisects an angle defined between the forward ray and the backward ray.
In accordance with the invention there is further provided an optical deflection switch for reducing an insertion loss comprising: a switching block of a light-transmissive material having a reflective surface and a second face, the second face including an input/output port and the reflective surface for providing reflection of a beam of light passing through the input/output port into the switching block, and wherein the switching block has an angle and a thickness such that a deflected beam is directed to one of a plurality of output ports of the optical deflection switch at normal incidence; a second block of light-transmissive material having a first face and a second face, the first face including an input port thereon for receiving a collimated beam of light and the second face for providing total internal reflection of the beam of light in a first switching state and for acting as an output/input port for optical communication with the input/output port of the switching block when the total internal reflection is frustrated in a second switching state; and a switch for selectively switching the device from the first switching state to the second other switching state.
In accordance with the present invention, there is provided an optical deflection switch comprising a switching block of light-transmissive material having a reflective surface and a transmissive face, the reflective surface for providing reflection of a beam of light passing through the transmissive face into the switching block to produce a first reflected beam; a second block of light-transmissive material having a first and a second face, the first face including an input port thereon for launching the beam of light into the optical deflection switch and the second face for providing total internal reflection of the beam of light in a first switching state to produce a second reflected beam and for providing input and output locations for optical communication with the transmissive face of the switching block when the total internal reflection is frustrated in a second switching state, and wherein the switching block is a tapered block having an angle and a thickness such that the first and the second reflected beam intersect each other and such that the first reflected beam is directed to a first output port at normal incidence and the second reflected beam is directed to a second output port at normal incidence, said first and second output port being in optical communication with the second block; and a switch for selectively switching the device from the first switching state to the second switching state.
Furthermore, the present invention provides an optical switch for switching an input beam of light to one of a plurality of output ports comprising a first lens for collimating the input beam of light to produce a collimated beam; a first refractor having an input face for receiving the collimated beam of light and a second face for reflecting the collimated beam of light by total internal reflection in a first switching state to produce a first reflected beam, and for allowing the collimated beam of light to pass therethrough by frustrating the total internal reflection in a second switching state; a second refractor having a transmissive face and a reflective surface, the reflective surface for reflecting the collimated beam of light passing from the second face through the transmissive face into the second refractor in the second switching state to produce a second reflected beam; and a second lens for focusing the first and the second reflected beam to produce a first and a second output beam, said first output beam being substantially parallel to said second output beam.
In accordance with another embodiment of the present invention the second refractor is a wedge having an angle and a thickness such that the first and the second reflected beam intersect each other, and such that the first and the second beam are directed to the plurality of output ports at normal incidence.